State 1
Reference

Figure 11. Overstory of Artemisia nova with an understory of Psuedoroegenaria spicata.

The reference state consists of three dominant plant communities: The black sagebrush (Artemisia nova) dominated community, the the mixed early sagebrush (Artemisia arbuscula ssp. Longiloba) and black sagebrush dominated community, and a community where overstory shrub canopy dominance is usurped by bunchgrasses. The greatest difference between the three plant communities is composition and foliar cover of sagebrush (Artemisia) species, and may include mountain big sagebrush (Artemisia tridentata ssp. Vasayana). Mountain big sagebrush foliar cover increases on sites that are closer to the high end of the effective precipitation range (15 to 19 inches) and the calcium carbonate equivalency in the soil is lower, closer to minimum 15 percent concentrations outlined in the site concept. Processes (both natural and anthropogenic) that result in state and community changes include fire, grazing, land use change, and occurrence of invasive species (Davies et al., 2011).

Characteristics and indicators. The shift between plant communities at this ecological site is generally driven by calcium carbonate concentration in soils, effective precipitation, and sagebrush killing disturbances or lack thereof. Historically, low to mixed severity fires occurred at relatively frequent fire return intervals of 10 to 25 years, limiting sagebrush canopy density and creating a mosaic of sagebrush stands and more open grasslands (Knick, Holmes, & Miller, 2005). Exclusion of fire (in conjunction with climate change) increases sagebrush canopy cover and can lead to more severe stand replacing fires, often times at more frequent intervals. These severe fires can drive shifts to grassland communities as well as create opportunities for invasive species establishment (Roadhouse, Irvine, & Bowerstock, 2020; Knick et al., 2005). Improper grazing practices can also lead to an increase in sagebrush canopy cover and increased risk of severe, stand replacing fire occurrence. Removal of understory grasses can lessen the opportunities for low severity fires which leads to increased canopy densities and increases potential for severe fire disturbance events (Knick et al., 2005).

Resilience management. This site has moderate to high resilience as a result of the cryic soil temperature regime and xeric soil moisture regime. Resistance and resilience of a specific site has been attributed with abiotic conditions favorable to plant growth and reproduction (Maestas et al. 2016). Soils that fall within the cryic (cold) temperature regime and xeric (wet) moisture regime tend to have higher diversity and production, and are therefore more resilient, specifically in terms of resisting or recovering from invasion post disturbance (Maestas et al., 2016). On the LRU scale, this site may also have increased resistance to invasion of annual grasses due to the calcium carbonate concentration found in the 10 to 25 centimeter range of the soil profile. Calcareous soils have shown to provide a deterrent to establishment of invasive grasses such as Bromus tectorum (Miller et al., 2006).

Community 1.1
Black Sagebrush and Bluebunch Wheatgrass

Figure 12. Black sagebrush as the dominant overstory with nearly equal canopy cover of bluebunch wheatgrass.

This community is well adapted to the abiotic conditions of the Lost River Mountain LRU, specifically when soils are shallow to a restrictive layer such as bedrock, clay, or calcareous soils. Although composition, foliar cover, and production at this ecological site can vary throughout the shrub overstory, black sagebrush tends to occur more often as a singular dominant overstory species. Black sagebrush thrives at dryer sites with soil conditions that create a root restrictive layer. The more pronounced these conditions become, the more likely the community shifts towards a black sagebrush dominated community (Tilley & St. John [2], 2012). At the landscape scale, mosaics between little and black sagebrush dominated sites can represent slight localized differences in soil conditions and effective precipitation (McArthur & Stevens, 2009). This community is drought tolerant and plant mortality is generally low during extended periods of below average precipitation. Black sagebrush communities can form in a mosaic distribution with other communities in this state (1.2 &1.3) across the range of effective precipitation. Black sagebrush dominated communities are more common at the lower end of the effective precipitation range (15 inches), and cover of alkali sagebrush tends to increase towards the upper end of 19 inches. Occasionally, at the upper end of the effective precipitation range, mountain big sagebrush can establish within the black and alkali sagebrush communities (Tilley & St. John [2], 2012). Surveys completed within this state and community had an average foliar cover of black sagebrush of 15 percent and bluebunch wheatgrass at 25 percent. Bluebunch wheatgrass is able establish on this site in openings not occupied by sagebrush. As a result of competition with sagebrush, bluebunch wheatgrass foliar cover decreases as sagebrush cover increases. Sagebrush cover tends to increase over time in the absence of disturbances such as fire, herbivory, or mechanical treatments (Davies, Bates, & O'Connor, 2021). Alternately, as sagebrush cover decreases, bluebunch cover increases resulting in bluebunch wheatgrass/dwarf sagebrush community (1.3).

Resilience management. This community is moderately resilient. Black sagebrush and bluebunch wheatgrass are both drought tolerant species, increasing their resistance to climate related disturbances such as prolonged periods with below average precipitation. However, with this community generally occurring on the drier end of the 15-19" effective precipitation range, recovery from other disturbances can be slow (Chambers et al., 2014). Slow returns to pre-disturbance conditions can open windows for erosion to occur and invasive species to establish. Additional resistance to invasion of annual grasses can be attributed to the calcareous soils. Calcareous soils, when high enough in the soil profile have shown to act as a deterrent towards establishment of invasive annual grasses (Miller et al., 2006).

Community 1.2
Little Sagebrush, Black Sagebrush and Bluebunch Wheatgrass

Figure 15. Even overstory composition of alkali and black sagebrush with a bluebunch wheatgrass understory.

Like community 1.1, this community is well adapted to the abiotic conditions of the Lost River Mountain LRU. As depth and concentration of the calcareous soil layer decreases, the likelihood of a mixed little and black sagebrush overstory increases. Although composition, foliar cover, and production at this ecological site can vary throughout the shrub overstory, little sagebrush density tends to increase towards the higher end of the effective precipitation range (Tilley & St. John [2], 2012). It is not uncommon to find communities within this ecological site dominated by little sage with little to no black sagebrush presence. Where this site enters the transition zone (near the 19 inch effective precipitation zone and calcium carbonate concentrations decrease or are deeper in the soil profile), presence of mountain big sagebrush (Artemisia tridentata spp. vaseyana) becomes more likely. At the landscape scale, mosaics between alkali and black sagebrush dominated sites can represent slight localized differences in soil conditions and effective precipitation (McArthur & Stevens, 2009). This community is drought tolerant and plant mortality is generally low during extended periods of below average precipitation. Mixed little and black sagebrush communities can form in a mosaic distribution with other communities in this state (1.1 & 1.3) across the range of effective precipitation. Little or mixed little and black sagebrush dominated sites are generally more common at the upper end of the effective precipitation range (19 inch) and as depth or strength of restrictive layer becomes less pronounced (Tilley & St. John [2], 2012).

Resilience management. Resilience in community 1.2 is slightly higher than community 1.1. Like black sagebrush, little sagebrush is a drought tolerant species able to withstand periods of below average precipitation. The presence of little sagebrush is often an indicator of a slight localized increase in effective precipitation over the pure stand of black sagebrush that is exhibited in community 1.1. Higher amounts of effective precipitation have been shown to increase resilience in rangeland communities (Chambers et al., 2014). Additionally, increasing biodiversity in the overstory canopy reduces the risk that insect or disease would impact the entire canopy.

Community 1.3
Bluebunch Wheatgrass and Low Sagebrush

This community is characterized by a change in dominant foliar cover from sagebrush (black sagebursh, little sagebrush, or a combination of the two) to a dominant foliar cover of bunchgrasses including bluebunch wheatgrass and Sandberg bluegrass. The shift in dominant foliar cover to bunchgrasses can be a result of local site characteristics that allow the bunchgrasses to establish and minimize additional growth of sagebrush, or by a sagebrush mortality event. These events can include fire, flooding, intense freezing periods, insect and disease, or anthropogenic disturbances. These sagebrush mortality events are low to moderate severity, leaving behind enough sagebrush plants to maintain a reduced population and seed source. Severe disturbance events that remove the majority or all of the sagebrush population in an area moves the ecological site into State Three, the Disturbance State. Production values for this community are wide ranging with the ability to outproduce communities 1.1 and 1.2 due to the increased opportunity for bunchgrass establishment. At the high end of the production range in this community (1200 pounds per acre), grasses can account for over half of total production (650 pounds per acre).

Resilience management. This community is moderate to highly resilient when bluebunch wheatgrass dominates the canopy cover and production. Bluebunch wheatgrass is well suited to the variable climate experienced in the Lost River Mountains and is resilient towards many natural disturbances including drought and frequent or severe fire. Bluebunch wheatgrass has shown to recover to pre-fire disturbance population levels in 1 to 7 years post disturbance. Under certain conditions, canopy cover and production can exceed pre-fire values (Zlatnik, 1999). Bluebunch wheatgrass is a decreaser, reducing in canopy cover and production in relation to grazing pressure. Under heavy grazing pressure the species will shift towards areas such as under the canopy of shrubs, opening the canopy for the establishment of rhizomatous grass species, invasive species, or bare ground. If grazing pressure is significant enough in intensity and duration resulting in chronic defoliation, this ecological site will shift to the Grazing Resistant State.

Pathway 1.1A
Community 1.1 to 1.2

Black Sagebrush and Bluebunch Wheatgrass

Little Sagebrush, Black Sagebrush and Bluebunch Wheatgrass

Community transition from community 1.1 to community 1.2 is generally a result of localized abiotic conditions relating to effective precipitation, as well as depth and concentration of calcareous soils. Black sagebrush tends to dominate sites where calcareous soils are stronger and closer to the surface. As calcium carbonate concentrations decrease, deepen, and precipitation conditions become closer to the 15 inch boundary of relative effective annual precipitation, the likelihood of alkali sage emigrating or becoming dominant increases. As these conditions become really pronounced (nearing transitional areas) mountain big sagebrush (Artemisia tridentata spp. vaseyana) can be present in the overstory.

Context dependence. The abiotic conditions that result in community transitions from 1.1 to 1.2 are site specific and not directly influenced by anthropogenic or biotic interactions.

Pathway 1.1B
Community 1.1 to 1.3

Black Sagebrush and Bluebunch Wheatgrass

Bluebunch Wheatgrass and Low Sagebrush

Community transition from community 1.1 to 1.3 is a result of a sagebrush removal disturbance. These disturbances can be either anthropogenic or naturally occurring. Natural disturbances include low to moderate severity fire, sagebrush die off events from freeze kill, drought, of prolonged saturation (flooding). Anthropogenic disturbances include mechanical or chemical brush thinning, land conversion, and herbivory.

Pathway 1.2A
Community 1.2 to 1.3

Little Sagebrush, Black Sagebrush and Bluebunch Wheatgrass

Bluebunch Wheatgrass and Low Sagebrush

Community transition from community 1.2 to 1.3 is a result of a sagebrush removal disturbance. These disturbances can be either anthropogenic or naturally occurring. Natural disturbances include low to moderate severity fire, sagebrush die off events from freeze kill, drought, of prolonged saturation (flooding). Anthropogenic disturbances include mechanical or chemical brush thinning, land conversion, and herbivory.

Pathway 1.3A
Community 1.3 to 1.1

Bluebunch Wheatgrass and Low Sagebrush

Black Sagebrush and Bluebunch Wheatgrass

Transitions from community 1.3 to community 1.1 would be a result of time without a sagebrush removing disturbance (fire, flood, freeze, or prolonged drought). Time needed for sagebrush communities to re-establish is dependent on localized climate conditions and relative resilience of the site.

Pathway 1.3B
Community 1.3 to 1.2

Bluebunch Wheatgrass and Low Sagebrush

Little Sagebrush, Black Sagebrush and Bluebunch Wheatgrass

Transitions from community 1.3 to community 1.2 would be a result of time without a sagebrush removing disturbance (fire, flood, freeze, or prolonged drought). Time needed for sagebrush communities to re-establish is dependent on localized climate conditions and relative resilience of the site.

State 2
Grazing Resistant

When a Shallow to Loamy, Calcareous ecological site enters the Grazing Resistant state, the primary shift occurs in the understory vegetation. Grazing pressure from livestock, native ungulates, or a combination of the two drives a shift from the cool-season bunch grasses present in the Reference State towards rhizomatous wheatgrasses, short-stature bunch grasses, and ground covering forbs. This state is generally a result of current or historic improper grazing practices that potentially included higher socking rates and repeated heavy grazing during the growing season.

Characteristics and indicators. In this state, total canopy cover and production values for mid to large sized bunchgrasses such as bluebunch wheatgrass will decrease. These understory grasses will be relegated to the protected areas under the sagebrush canopies where they are sheltered from grazing. As they are removed from the canopy gaps, they will be replaced with grazing resistant short-stature bunch grasses like Sandberg bluegrass (Poa secunda) and rhizomatous wheatgrasses such as thick spike wheatgrass (Elymus lanceolatus), Western wheatgrass (Pascopyrum smithii), and at the higher end of the precipitation range, slender wheatgrass (Elymus trachycaulus). Openings in the canopy gaps vacated by bunchgrasses also present opportunities for an increase in disturbance tolerant forbs such as Hood's phlox (Phlox hoodii), cushion phlox (Phlox pulvinata), vetch species (Vetch sp.) and Indian paintbrush species (Castilleja sp.). Opportunities for invasive annual grasses also increase as competition from native grasses is removed from the canopy gaps. Depending on how well grazing resistant rhizomatous and bunchgrasses occupy the canopy gaps, an increase in bare ground cover usually occurs. This can lead to increased erosion and decreased infiltration, decreasing available moisture. Because of this, productivity and canopy cover will be lower than at the Reference State.

Resilience management. Resilience in this state is lower than in the Reference State, primarily due to the decrease in available moisture and the opportunity for invasive species recruitment. Ability to recover from disturbance in rangeland systems has shown to be related to local climatic conditions. As available moisture increases and temperature decreases, resilience to disturbance increases (Chambers, et al. 1014). At this ecological site, resilience of the black and little sagebrush dominated sites would tend to be lower than at the sites with mountain big sagebrush in the overstory canopy as this would indicate higher available moisture and lower average annual temperature. Resilience to erosion and invasive species establishment would be dependent on how well rhizomatous grasses and forbs occupy the bare ground spaces left by the removal of bunchgrasses. Rhizomatous grasses are mat forming and if able to establish relatively quickly can aid in reducing erosion. Additionally, if native rhizomatous grasses and forbs are able to quickly establish, this decreases the ability of invasive annual grasses such as cheatgrass to occupy bare soil openings within the site.

Community 2.1
Sagebrush, Short Stature Bunchgrass, and Rhizomatous Wheatgrass

This plant community is identified by its sagebrush overstory and diminished short stature bunch grass and rhizomatous wheatgrass understory. The shrub overstory will consist of black sagebrush, little sagebrush, mountain big sagebrush, or a combination of any of the three, depending on available site moisture and elevation. Within this state and community, the bluebunch wheatgrass dominated understory present in the reference state is replaced by short stature bunch grasses such as Sandberg's bluegrass, and rhizomatous wheatgrasses. Remaining bluebunch wheatgrass is concentrated tightly under sagebrush canopies where it is protected from grazers. Sagebrush canopy cover will often be higher than that of the reference state as opportunities for sagebrush to migrate into the openings left by previous bluebunch wheatgrass plants are created. Sagebrush canopy cover in the reference communities ranges between 3-29% and 14-30% in the grazing resistant community. The diminished understory in this community also leads to lower annual production values. Production in the reference state ranges from 490-803 lbs/ac, whereas production in the grazing resistant community ranges from 320-500 lbs/ac. The greatest difference is caused by the decrease in bluebunch wheatgrass density. Bluebunch wheatgrass accounts for 90-450 lb/ac in the reference communities, and decreases to 0-50 lbs/ac in the grazing resistant community.

Resilience management. This community has moderate resilience, mostly in relation to the understory grass species that replace bluebunch wheatgrass in the reference communities. Sandberg bluegrass is a highly drought resistant species of bunchgrass that is also resistant to grazing stress. Even when tilled, Sandberg bluegrass is able to re-establish to pre disturbance levels within 7 years (Howard, 1997). Although not as resilient to grazing pressures as Sandberg bluegrass, the rhizomatous wheatgrasses that can occur on this site can tolerate moderate grazing. On upland sites, Western wheatgrass is considered to be a decreaser under heavy grazing pressure when annual precipitation is under 20", however, switches to an increaser when annual precipitation is over 20" ( Tirmenstein, 1999). Alternately, resilience in this community is lowered through the decrease in available soil moisture that occurs from the shift to rhizomatous grasses and the increase in bare soil cover. This is more prevalent on the sites that occur in the lower end of the effective precipitation range (15"). Sites closer to the 19" end of the precipitation range will be more resilient as a result of the additional moisture availability (Chambers, 2014).

State 3
Disturbed

Figure 21. Shallow to Loamy Calcareous 15-19" site that was burned in a fire in 1977, removing majority of early sagebrush overstory and increasing bunchgrass understory.

The Disturbed state is a result of both natural and anthropogenic disturbance events that result in widespread sagebrush mortality. The primary natural disturbance resulting in sagebrush mortality at this ecological site is frequent or severe wildfire. Flooding, intense freeze events, and insect and disease can also occur. Because this LRU exists primarily on publicly managed lands (US Forest Service, Bureau of Land Management, and State), widespread anthropogenic disturbance events are infrequent. Examples of anthropogenic disturbance events include brush management through sagebrush mowing or removal treatments, chemical treatments, or improper grazing techniques that result in high intensity hoof disturbance. A combination of natural and anthropogenic disturbance is possible and can result in increased severity of disturbance, decreased resilience, and greater difficulty returning to the Reference State. For example, improper grazing practices that result in chronic defoliation following a fire disturbance event can increase bare ground cover, increase erosion potential, and slow the reestablishment of grass species that preclude the return of overstory sagebrush canopy (Zlatnik, 1999).

Characteristics and indicators. The primary indicator of the Disturbed State is near to complete loss of overstory sagebrush species (black sagebrush, little sagebrush, and mountain big sagebrush). A shift towards an increase in native and non-native disturbance tolerant grasses and forbs is likely with removal of resource competition associated with sagebrush overstory. Additionally, canopy cover of disturbance tolerant shrubs such as yellow rabbitbrush (Chrysothamnus viscidiflorus) and rubber rabbitbrush (Ericameria nauseosa) may increase. Severe disturbance events also increase the opportunity for invasion of annual grasses and weeds such as cheatgrass (Bromus tectorum) and thistle species. Percent canopy cover of invasive species is dependent on distance of a seed source post disturbance. Initial cover of invasive species stays below 5 percent (Zlatnik, 1999).

Resilience management. Resilience in this state is moderate. Many of the post-disturbance grasses and shrubs that are common in this state establish quickly and reach a representative canopy within 10 years post-disturbance, and continue to increase until overstory canopy of sagebrush begins to return. However, local resilience in this state is highly dependent on current soil moisture availability, seed sources, timing and severity of the disturbance. In the instance of fire disturbance, bluebunch wheatgrass mortality can be significantly lower if the fire occurs in the spring as opposed to fall, and recovery can be impacted by quantity of immediate post-fire precipitation (Zlatnik, 1999). More severe disturbances increase possibility of post-disturbance invasion. The greater the establishment of invasives, the lower the site resilience becomes.

Community 3.1
Mixed Grass and Forb

The Mixed Grass and Forb community is driven by the disturbance related removal of the primary overstory of sagebrush species. Both natural and anthropogenic disturbances that result in complete or near to complete removal of the sagebrush overstory create opportunities for increased establishment and canopy cover of both native and non-native grasses and forbs, as well as disturbance tolerant shrubs. Fire is the primary disturbance responsible for removing sagebrush at this ecological site. The frequency and severity of fire disturbances are highly influenced by the overstory composition of the specific site in the Reference state. The composition and extent of the sagebrush species in the overstory impacts that respective fire regime. At sites dominated either solely by black sage, alkali sage, or varying combinations of the two, fire return intervals are less frequent. Additionally, fires are usually low to moderate in severity and cover small spatial extents (Steinberg, 2002 & Fryer, 2009). Black and alkali sagebrush dominated communities often lack fuels sufficient for frequent fire return intervals, severe fire events, or large fire events (Fryer, 2009). Shallow to loamy calcareous sites that are at the higher end of the 15 to 19 inch precipitation range with an overstory canopy at least partially comprised with mountain big sagebrush are more susceptible to frequent fire return intervals, more severe fires, and often at a greater extent. Sites dominated by mountain big sagebrush communities have historically burned more frequently than sites dominated by other sagebrush species because the soil moisture and temperature regimes required by mountain big sagebrush are also more apt to produce an increased amount of fine fuels from other plant species (Innes, 2017).

Resilience management. This plant community is moderately resilient because the grasses and forbs that dominate the composition are resistant to a variety of disturbances and able to re-establish quickly in the event of more severe disturbances. Both bluebunch wheatgrass (Pseudoroegenaria spicata) and Sandberg's bluegrass (Poa secunda) are rarely harmed by fire events except for in the most severe instances. Both species are able to reduce the amount of heat transfer to the root systems, allowing post-fire regrowth (Zlatnik, 1999 & Howard, 1997). Studies have shown that in the absence of grazing, bluebunch wheatgrass dominated systems are able to return to pre-fire production levels eight years post disturbance (Zlatnick, 1999). Sandberg bluegrass has been shown to fully re-establish post-plowing disturbance events in as little as seven years after the plowing (Howard, 1997). Although many of the species in this state are at least somewhat resilient towards many of the disturbances encountered, available soil moisture, weather, and rest from grazing all play an important role in how quickly a site can recover post-disturbance. Both of the common shrub species found in this community at varying compositions are not only disturbance tolerant, but tend to increase with disturbance. Both yellow rabbitbrush and rubber rabbitbrush are often the first shrub species to re-establish on this ecological site following a disturbance, and can increase in relation to the severity or frequency of the disturbance. Although yellow rabbitbrush exists in relatively small numbers within the Reference State, it can only become the dominant shrub species in highly disturbed systems (Terminstein, 1999).

Transition T1A
State 1 to 2

Reference

Grazing Resistant

Transition from the Reference state to the Grazing Resistant state is a product of current or historical improper grazing practices that resulted in chronic defoliation of vegetation. Continual overstocking and overgrazing during critical growing periods can result in a significant functional and compositional shift in the understory vegetation of the Shallow to Loamy Calcareous ecological site. In perennial bunchgrasses such as bluebunch wheatgrass which is the dominant understory vegetation in the Reference State, repeated overgrazing weakens the underground structures through undernourishment caused by the continual removal of photosynthetic tissue (Daubenmire, 1940). This eventually results in death of these grasses, opening the canopy for grazing resistant grasses like Sandberg bluegrass, or bare soil. Because most of this LRU exists on publicly managed lands with regulated grazing policies, new transitions to this state are rare. Historical practices and regulations may have differed, leading to current existence of this state.

Constraints to recovery. Constraints to recovery include: o Continued improper grazing techniques o Prolonged periods of drought that diminish regeneration of desired species o Loss of nutrient rich top soil due to increased erosion o Establishment of invasive species

Context dependence. Restoration efforts can be greatly influenced by precipitation patterns. Successful regeneration of Reference State understory species is highly dependent on moisture received post restoration efforts. Rates of successful establishment of bluebunch wheatgrass and Sandberg bluegrass increase when available moisture is high during critical regeneration periods (Zlatnik, 1999 & Howard, 1997).

Transition T1B
State 1 to 3

Reference

Disturbed

Transition from the Reference to the Disturbed State is primarily a mechanism of severe disturbance, both natural and anthropogenic. In this this ecological site, the most likely disturbance to cause this transition is frequent or severe wildfire events. Other disturbances include but are not limited to flooding, freeze kill, insect and disease, and mechanical brush removal.

Constraints to recovery. Primary constraint to recovery is distance to seed source. When the disturbance is severe enough and the extent is great, seed source populations for sagebrush species may be removed from the vicinity. In this case, immigration and re-establishment of overstory sagebrush species can be slow. This time period can be greatly reduced through seeding and planting interventions.

Context dependence. The primary factor driving likelihood of restoration success is post disturbance weather patterns. Prolonged period of drought can slow restoration processes, whereas average to above average precipitation post disturbance can greatly increase speed and success in re-establishment of sagebrush species (Robin, 2017; Steinberg, 2002; and Fryer, 2009).

Restoration pathway R2A
State 2 to 1

Grazing Resistant

Reference

The primary mechanism of restoration back to the Reference State is time without grazing. Seeding of desired Reference State species can speed up the restoration process.

Context dependence. Time frame for restoration is highly dependent on variations in localized weather patterns. Prolonged periods of drought can dramatically increase time required to return to the Reference State, whereas periods of above normal precipitation can decrease that time frame. Grazing practices that are infrequent and of light intensity, mimicking natural historic grazing patterns will not impact the restoration pathway. However, continuous early season grazing at moderate to high intensity resulting in significant defoliation will perpetuate the Grazing Resistant State.

Transition T2A
State 2 to 3

Grazing Resistant

Disturbed

Transition from the Grazing Resistant to the Disturbed State is a result of moderate to severe sagebrush removing disturbances. These can include both natural and anthropogenic disturbances; however, unlike the Reference State, possibility of moderate to severe fire events is reduced as a result of the diminished understory present in the Grazing Resistant State.

Restoration pathway R3A
State 3 to 1

Disturbed

Reference

The most important mechanism driving restoration from the Disturbed to the Reference State is time without sagebrush removing disturbances and distance from overstory species (sagebrush) seed source. Seeding or planting of desired overstory species in the Reference State can accelerate restoration efforts.

Context dependence. Restoration is highly dependent on time without disturbance. New sagebrush seedlings that are able to establish on a site are moderately sensitive to disturbances such as flood, freeze, and insect and disease. They are highly sensitive to herbivory and even low severity fire occurrence (Fryer, 2009 & Steinberg 2002). Seeding and planting of desired species can speed up the restoration process, however, regeneration success with or without planting is highly dependent on localized weather patterns during this restoration period. Periods of drought will slow the process significantly, whereas periods of above normal precipitation aid in sagebrush regeneration and establishment (Innes, 2017; Steinberg 2002 & Fryer, 2009).

Transition T3A
State 3 to 2

Disturbed

Grazing Resistant

Transition from the Disturbed to the Grazing Resistant State results from improper grazing practices that result in chronic defoliation. Plant communities in the Disturbed State are particularly vulnerable to heavy grazing in the years immediately following the disturbance that initiated the transition. If bunchgrasses are unable to establish, plant composition could shift to more grazing resistant, rhizomatous grass species.

Context dependence. Years of drought or below average precipitation in combination with improper grazing that results in chronic defoliation can accelerate transition to the Grazing Resistant State.